Technical Field
Internal combustion engines having rotating cylinder assemblies.
Description of Related Art
Despite the ongoing advances made in energy conversion devices, the piston-based internal combustion (IC) engine remains in widespread use as a power plant for automobiles and industrial applications. It appears that the IC engine will continue to have widespread use well into the future, particularly because there remains considerable opportunity to improve its energy conversion efficiency, as well as other operational aspects.
The vast majority of IC engines currently in use have an “in-line” configuration of cylinders. Such an IC engine may have a single block of cylinders having pistons operatively connected to a crankshaft by rods, or an IC engine may have a pair of blocks of cylinders formed in a V configuration in an engine block, each of the cylinders having pistons operatively connected to a single crankshaft by rods. “V8” engines, as well as “V-twins” (two cylinder), V4s, V6s, V10s, and V12s have this configuration, and are in use today.
In an alternative configuration, an IC engine may have a rotary configuration in which a block of cylinders is connected to a central crankshaft by rods. In operation of a rotary IC engine, the entire block of cylinders rotates. The pistons of the cylinder block are connected to the crankshaft by rods, and undergo reciprocating motion during a combustion cycle, thereby causing rotation of the crankshaft and the block of cylinders.
The rotary piston engine had substantial use in early IC engine driven aircraft, but was eventually rendered obsolete by advances in alternative power plants, including turbine-based propulsion. Rotary piston engines of that era had high fuel consumption and high oil consumption. Additionally, air drag from the rotating cylinder assembly increases with the square of rotational speed, which limited the maximum RPM at which these engines could operate, thus limiting maximum power output.
Rotary engines, much like conventional in-line fixed block engines, also have undesired complexity in the components required to provide the intake of combustible air/fuel mixture, and the supply and timing of ignition energy. Most rotary engines are configured to operate with multiple spark ignition sources disposed around the rotating cylinder assembly. The timing of these ignition sources in the combustion cycles of the cylinders must be managed, adding further complexity. Additionally, many rotary engine configurations are limited to operating as two-cycle engines due to their intake and exhaust designs.
However, despite these problems, the rotary piston IC engine has certain inherent advantages over the in-line stationary cylinder block engines in single and V-configurations. Because of the lack of a heavy crankshaft as used in in-line fixed block engines, rotary piston engines run with less vibration. They also have a high power-to-weight ratio. Additionally, the rotary piston assembly itself acts as a flywheel; thus there is no need to add the rotating mass of a solid plate flywheel, as is done in conventional in-line fixed block engines. If at least some of the problems could be solved by a rotary IC engine having an improved design, the rotary IC engine could become a valuable alternative power plant for automobiles and industrial applications, acting as a bridge to alternative energy conversion and transportation devices that will not be commercialized until well out in the future.